Echo when you would have learned, but you are immune:
You can't learn the nuances of hand to hand since you are immune to a water elemental!

Echo when you would have learned but your victim is immune:
You can't learn the nuances of dagger since a dryad is immune!

Echo when you are wielding a weapon you don't know:
You are spending more time focusing on a fist of lightning, to even attempt to learn the nuances of nova!